1. Field of the Invention
The present invention relates to an apparatus for manufacturing a thermal transfer recording medium which is used in a thermal transfer recording apparatus, the thermal transfer recording apparatus being utilized as an output terminal device of an information processing apparatus such as a word processor or a facsimile, and also to an apparatus for renewing (recondition) a thermal transfer recording medium in which ink is applied to a previously-used thermal transfer recording medium so that the thermal transfer recording medium can be reused numerous times.
2. Description of the Related Art
At present, various types of printers are used as output terminal devices for information processing apparatuses such as word processors, facsimiles, or computers. These printers employ various recording technologies such as a thermal transfer, electrophotography, ink jet, and wire dot technologies.
Among these recording technologies, thermal transfer printers, which use a heat generating resistance array called a thermal head, are widely used in the prior art because of their silent operation, low cost, miniaturization adaptability, simple operability and high reliability. In recent years, the use of thermal transfer printers has extended from business use to home use, and further to hobby use.
The thermal transfer systems are broadly classified into two types; (1) a fusion type thermal transfer system where ink from a thermal transfer recording medium (such as an ink ribbon) is melted (fused) by heat from a thermal head and transferred to a recording paper made of ordinary paper and (2) a sublimation type thermal transfer system where heat sensitive paper is colored by the heat from a thermal head. At present, the fusion type thermal transfer recording system is mainly used because of its low price.
FIG. 7 shows the basic principle of the above-mentioned fusion type thermal transfer system and the basic configuration of a thermal transfer recording medium used in the fusion type thermal transfer system. As shown in FIG. 7, a thermal transfer recording medium 1, which is generally called an ink ribbon or an ink sheet, is structured such that an ink layer 1b is laminated onto a substrate 1a.
A high molecular resin film having thickness of 1 to 12 .mu.m is usually used in the substrate 1a of the above-mentioned thermal transfer recording medium 1. The substrate 1a is composed of general-purpose resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyether ether ketone (PEEK), and aramid.
On the rear surface of the substrate 1a, a lubrication layer 1e is generally applied in order to reduce abrasion caused by sliding contact of a thermal head against the thermal transfer recording medium, to stabilize transfer of an ink ribbon between bobbins (when an ink ribbon is used as the thermal transfer recording medium), and to prevent the substrate 1a from adhering to the ink layer 1b of the ink ribbon when the ink ribbon is wound on the bobbins.
The main components of the ink layer 1b of the above-mentioned thermal transfer recording medium 1 are a thermal fusing material, such as low melting wax, and a thermal fusing resin which performs well in close contact with the recording paper. Various types of pigments are used as a coloring agent and various types of plasticizer, dispersant, antioxidant and the like are added in small quantity.
The low melting wax used in the ink layer 1b may be, for example, carnauba wax, candelilla wax, rice wax, paraffin wax, microcrystalline wax, and polyethylene wax. These low melting waxes are used alone or in a mixed state.
The thermal fusing resin used in the ink layer 1b may include: (1) ethylene series copolymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl butyrate copolymer and ethylene-acryl copolymer; (2) poly(meth)acrylic esters such as polylauryl methacrylate and polyhexyl acrylate; and (3) vinyl chloride series copolymers such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer and vinyl chloride-vinyl alcohol copolymer. These resins are used alone or in a mixed state.
A thermal head 4 is pressed against the rear side of the substrate 1a of the thermal transfer recording medium 1, that is, from the side of the lubrication layer 1e. This causes the thermal transfer recording medium 1 to contact a recording paper 5. A heat generating resistance element 4a, located at a position corresponding to the desired record, generates heat, thereby fusing or softening ink at a position corresponding to the heat generating resistance element 4a such that the fused or softened ink is transferred onto the recording paper. The desired record is therefore obtained by the transferred ink 6.
However, with respect to a thermal transfer recording medium of such a thermal transfer system, once transfer recording is carried out, the thermal transfer recording medium must be thrown away because ink at the position corresponding to the transferred image is removed and thus the thermal transfer recording medium is in a defective state. Therefore, a problem arises because the operating costs of such a thermal transfer system become significantly high.
In order to solve such a problem, a thermal transfer recording medium capable of being used numerous times and a method of renewing a used thermal transfer recording medium have been proposed in the prior art.
FIG. 8 shows an example of a prior art thermal transfer recording medium (ink ribbon) capable of being used numerous times. This ink ribbon is generally called a multi-time ribbon and has been reduced to practice already.
The structure of this multi-time ribbon, as shown in FIG. 8, is such that an ink layer 1b is formed through repeated lamination of individual ink layers. The several layers are transferred in sequence from the upper layer during sequential printing operations, thereby realizing numerous recording operations from a single ribbon. In the example shown in FIG. 8, the ink layer 1b is constituted of ink layers 1b.sub.1, 1b.sub.2 in two layers. When such an ink ribbon is used in the printing operation for the first time, the ink layer 1b.sub.1 is used for printing. When the ink ribbon is used in the printing operation for the second time, the remaining part of the ink layer 1b.sub.1, that was not transferred in the first printing operation, and the ink layer 1b.sub.2 are used for printing.
With respect to the surface of the thermal transfer recording medium 1, after transfer of the first time as shown in FIG. 8, level differences are produced between a portion from which ink is transferred and a portion from which ink is not transferred. Therefore, since the surface of the ink layer 1b is uneven, close contact between the recording paper 5 and the ink layer 1b of the thermal transfer recording medium 1 is deteriorated during the second printing operation. This creates a problem in that every time the printing is repeated, the printing quality gradually deteriorates. Consequently, from the viewpoint that the goal is to maintain quality while reducing the operating cost, this method falls short.
This also sets a limit on the number of ink layers laminated on the ink ribbon, and thus the number of printing operations per ink ribbon, because the unevenness increases as the number of ink layers increases.
An example of a prior art method for renewing a thermal transfer recording medium is proposed in Japanese Patent Laid-Open No. Hei 6-286333 (1994). According to this method, a corona charging processing is applied to the ink layer of a used thermal transfer recording medium such that powder toners adhere to an ink lacking portion of the ink layer where ink has been removed due to a previous printing operation. The adhered powder toners are then fused by heat, and then a uniform leveling processing is carried out, thereby renewing the thermal transfer recording medium into a reusable state.
In this renewing method, however, since corona charging is utilized in similar manner to that used in a common electrophotography apparatus, a high voltage source is required. This causes a problem because the size of the apparatus is large and the cost inevitably becomes high.
Since the toners to be used in the renewing of the ink layer are powders, it is difficult to make the grain size of the toners uniform. A problem also exists in that since the charge quantity of toners is significantly dependent on humidity, control of the adhering amount of toners is quite difficult.
Further, since the average grain size of toners is about 10 .mu.m, a problem exists because, from the viewpoint of size, it is difficult for the powder toners to fill the ink lacking portions (having a size on the order of several .mu.m) of an ink layer with high precision.